Conventionally, in a centrifugal chiller, an HFC refrigerant, such as R134a refrigerant, is used as the refrigerant. HFC refrigerants belong to high-pressure refrigerants, and are known to have a high global warming potential (GWP). Given this, recently, in order to reduce environmental impact, attention is being given to the R1233zd(E) refrigerant, which is an HCFO (hydrochlorofluoroolefin) refrigerant, and its adoption in centrifugal chillers is being considered. The R1233zd(E) refrigerant is a low-pressure refrigerant and is known for its low density.
Further, in a centrifugal chiller that uses a high-pressure refrigerant, vessels utilized for constituent devices, such as a condenser, an evaporator, an economizer, and a subcooler, pressure vessels are required, and their strength is secured by using circular drums. As a result, each of the constituent devices is configured using an independent vessel, and a configuration is adopted in which each of the vessels is arranged independently. Meanwhile, when a low-pressure refrigerant is used, since the strength of the vessels in each of the constituent devices can be decreased, the circular drum need not necessarily be used, and a square drum or the like can be selected, for example. In Patent Document 1, a single-drum type centrifugal chiller is disclosed in which vessel walls are shared.
Patent Document 1 is an application made at a time when specified fluorocarbon refrigerants (HCFC refrigerants), which are low-pressure refrigerants, were used, and discloses a centrifugal chiller that is made more compact by integrating a plurality of devices by sharing the vessel walls of the various constituent devices. HCFC refrigerants include the chlorine group, their ozone depletion potential (ODP) is high, and they are considered to be a weapon contributing to the depletion of the ozone layer. From this, there has been a history of HCFC refrigerants being replaced by HFC refrigerants, which are high-pressure refrigerants. As a result of this, there has been a trend to use circular drums that can secure a high degree of strength as the vessels of the various constituent devices.